Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare this is a non-read-only, non-destructive, non-idempotent write. The description adds the real behavioral payload: what true vs false mean per channel and the consent condition for re-enabling a channel. It does not cover permission requirements or whether unspecified channels are left untouched.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Two tight sentences, front-loaded with the action and the channel set, then the usage rule. Every clause carries information; nothing is filler.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a mutation tool with no output schema, the description supplies the action, the value semantics, and the consent guidance an agent needs. The remaining gap is whether only supplied channels change (partial update) and whether at least one channel must be provided.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 0%, so the description must carry parameter meaning, and it does explain the boolean semantics for all six channel flags (email, sms/texts, call, whatsapp, gmb, fb) plus the opt-out intent behind false. It leaves contact_id and the partial-update question (what happens to channels not passed) unexplained.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource ('mark one contact reachable or Do Not Disturb') and enumerates the six channels, which is concrete enough that an agent can distinguish it from crm_save_contact or crm_tag_contacts. It does not explicitly name a sibling it should be used instead of, so it stops short of a 5.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives an explicit trigger ('when someone unsubscribes or asks not to be texted — set that channel to false') and an explicit caution for the inverse ('setting true... only do that if they asked'). Both the when and the when-not are stated, which is exactly what routing guidance should do.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.